News channels are abuzz once again with rumours of a Microsoft-Yahoo link-up. Only this time, it's not a complete change of ownership but an advertising partnership. Competitive stress in an industry dominated by Mountain View-based Google may have pushed the two rivals, who have plenty of bad blood between them, towards each other again.

CEO Jerry Yang, who started Yahoo, suffered from these battles and ultimately surrendered the corner office, returning to his erstwhile title of ''Chief Yahoo.'' The company brought in former Autodesk boss Carol Bartz as CEO. Microsoft CEO Steve Ballmer has already had a meeting with Bartz to discuss possible partnership areas and said he was not averse to a tie-up.(See: Yahoo has new CEO, Carol Bartz andMicrosoft still keen on slice of Yahoo: Ballmer)

Google, meanwhile, is also making an entry into the display advertising market, threatening the longer-standing display businesses of both Yahoo and Microsoft.